Flexible temperature sensor for lithium battery safety monitoring and preparation method thereof

Abstract

The invention discloses a flexible temperature sensor for lithium battery safety monitoring and a preparation method thereof. The flexible temperature sensor comprises a flexible substrate, an electrode, a temperature-sensitive film and a passivation layer, a polyimide film is used as the substrate, and an interdigital electrode is prepared on the surface of the substrate; mixing a reaction source with a solvent to form ink, and performing ink-jet printing on the surface of an electrode to obtain a patterned precursor film; and carrying out sintering reaction treatment on the precursor film by using a tubular furnace to obtain the temperature-sensitive film. And spin-coating a polyamide acid solution on the temperature-sensitive film and performing dehydration cyclization to generate a polyimide passivation layer to obtain a polyimide-packaged flexible temperature sensor which is attached to the outer surface of a lithium ion battery and is used for wearable contact detection of the battery. The flexible temperature sensor is insensitive to oxygen, strain and the like, the influence of environmental factors on the performance of the sensor is avoided, the temperature detection precision can be remarkably improved, the battery temperature can be monitored in real time, and the flexible temperature sensor is used for achieving battery safety management.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery monitoring, and in particular relates to an oxidation-resistant, strain-insensitive flexible temperature sensor for lithium battery safety monitoring and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are indispensable energy storage devices in modern society, widely used in mobile phones, electric vehicles, drones, and other fields. With the development of electric vehicles, mobile devices, and renewable energy, lithium-ion batteries are becoming an important strategic energy source. However, they also pose safety concerns. Lithium-ion batteries are prone to frequent fires, and once a single cell experiences thermal runaway, it can quickly create a significant explosion hazard. Therefore, safety monitoring of lithium-ion batteries for thermal runaway is essential.

[0003] Commonly observed indicators during thermal runaway include surface temperature, temperature rise rate, voltage drop, outgassing, mass loss, gas release, and fire. The internal and surface temperature of lithium-ion batteries is one of the most important parameters for monitoring thermal runaway. Existing wearable flexible temperature sensors inevitably bend as the battery deforms during thermal runaway temperature measurement. The sensor's structure and sensitive electrode materials make it difficult to decouple strain from temperature, thus affecting measurement accuracy. Furthermore, the temperature-sensitive layer may oxidize at high temperatures. Therefore, improving the flexible temperature sensor's resistance to oxidation and strain interference during temperature measurement is crucial. Therefore, developing wearable battery sensors that are oxidation-resistant and strain-insensitive holds great promise. Molybdenum disulfide and polyimide are promising materials for developing these flexible temperature sensors. Through material manipulation and structural design, flexible temperature sensors with oxidation-resistant and strain-insensitive battery surfaces can achieve excellent detection performance. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art by providing an oxidation-resistant, strain-insensitive flexible temperature sensor for lithium battery safety monitoring and a method for its preparation. This method is simple to prepare and utilizes wearable battery contact detection, improving detection accuracy while avoiding contact with the harsh internal battery environment, extending the sensor's service life, and enabling battery temperature monitoring and safety status monitoring.

[0005] The technical solution adopted by the present invention is:

[0006] A flexible temperature sensor for lithium battery safety monitoring comprises a flexible substrate; electrodes are deposited on the flexible substrate; a temperature-sensitive precursor film is inkjet printed on the electrode and annealed to obtain the temperature-sensitive film; and a passivation layer is covered on the surface of the temperature-sensitive film.

[0007] Optionally, the preparation of the temperature-sensitive film includes: dissolving ammonium tetrathiomolybdate and / or ammonium tetrathiotungstate in a mixed solvent of water, propylene glycol and ethanol to prepare ink; inkjet printing the prepared ink on an electrode of a flexible substrate to form a precursor film; after removing the organic solvent from the precursor film, annealing it at a temperature of 400-500°C in an atmosphere of Ar60 sccm and H2 20-40 sccm to obtain a temperature-sensitive film.

[0008] Optionally, the volume ratio of water: propylene glycol: ethanol is 1:1.5:2.5; and the amount of ammonium tetrathiomolybdate and / or ammonium tetrathiotungstate added is 6 mg / ml.

[0009] Optionally, the substrate temperature of the inkjet printing is 30-60° C., the solvent evaporation time is 20-60 min, the number of inkjet layers is 15-20 layers, and the ink droplet spacing is 10-30 μm.

[0010] Optionally, the passivation layer is a condensation-type polyamic acid layer, and the preparation method includes: under anhydrous and N2 atmosphere, TPEQ is completely dissolved in DMF, PMDA is added and continued to stir, and the above steps are repeated twice to obtain a polyamic acid solution; the polyamic acid solution is spin-coated on the surface of the temperature-sensitive film, and then the temperature is increased to remove the solvent and the polyamic acid is thermally imidized and ring-closed.

[0011] Optionally, the spin coating parameters are 500 rpm, 5 s; 4000-8000 rpm, 60 s; and the step temperature rise is programmed to 70°C, 1 h, 150°C, 2 h, 200°C, 1 h, and 250°C, 1 h.

[0012] The preparation method of any flexible temperature sensor for lithium battery safety monitoring described in the present invention comprises: using a polyimide film as a flexible substrate; vacuum evaporating a metal film and using laser direct writing to obtain an electrode; mixing a reaction source and a solvent to form an ink, printing it on the electrode surface according to a designed pattern, heating until the organic solvent evaporates to obtain a patterned precursor film, and annealing to obtain a temperature-sensitive film; preparing a condensation-type polyamic acid based on a "two-step method", spin-coating the polyamic acid on the surface of the temperature-sensitive film and dehydrating and cyclizing it to generate a polyimide passivation layer, thereby obtaining a flexible temperature sensor encapsulated by the polyimide film.

[0013] Optionally, the electrode is an interdigital electrode with a thickness of 30 to 500 nm, and the material is at least one of chromium, nickel, gold, platinum and copper; the temperature-sensitive film covers the working end of the interdigital electrode.

[0014] Optionally, the laser direct writing parameter power is 5% to 15%, and the speed is 1000 mm / s.

[0015] Optionally, the preparation of the temperature-sensitive film includes: dissolving ammonium tetrathiomolybdate and / or ammonium tetrathiotungstate in a mixed solvent of water, propylene glycol and ethanol to prepare ink; the prepared ink is inkjet printed on the electrode of the flexible substrate to form a precursor film; after removing the organic solvent from the precursor film, the precursor film is annealed at a temperature of 400-500°C in an atmosphere of Ar60 sccm and H2 20-40 sccm to obtain a temperature-sensitive film; the passivation layer is a condensation-type polyamic acid layer, and the preparation method includes: in an anhydrous and N2 atmosphere, TPEQ is completely dissolved in DMF, PMDA is added and continued to stir, and the above steps are repeated twice to obtain a polyamic acid solution; the polyamic acid solution is spin-coated on the surface of the temperature-sensitive film, and the solvent is removed by step heating and the polyamic acid is thermally imidized and ring-closed.

[0016] The advantages of the present invention are:

[0017] 1. This invention detects temperature parameters by changing the sensor's resistance due to changes in the battery's internal temperature. The interdigitated electrode design allows for simple and low-cost fabrication, flexible manufacturing processes, and excellent sensitivity and stability. The polyimide passivation layer offers advantages such as high-temperature resistance, oxidation resistance, strong wearability, and resistance to corrosion in complex battery environments, providing a new solution for battery safety monitoring.

[0018] 2. The present invention has good flexibility and adaptability, adopts inkjet printing technology, and has high temperature resistance. It can not only be used in the field of lithium batteries, but also has broad application prospects in harsh detection environments such as new energy batteries, aircraft engines, and rescue robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0020] Figure 1 Schematic diagram of the device structure of the present invention;

[0021] Figure 2 is the Raman spectrum of the temperature sensitive material film of the present invention;

[0022] Figure 3 Schematic diagram and optical photograph of the interdigitated electrode in the present invention;

[0023] Figure 4 It is a physical diagram of the present invention;

[0024] Figure 5 It is the temperature performance test of the present invention;

[0025] Figure 6 It is the strain performance test of the present invention;

[0026] Figure 7 It is the antioxidant performance test of the present invention;

[0027] Figure 8 This is a physical diagram of the present invention for monitoring the overcharge safety status of soft-pack lithium batteries;

[0028] Figure 9 This is a temperature test diagram for monitoring the overcharge safety status of soft-pack lithium batteries according to the present invention;

[0029] Figure 10 This is a physical diagram of the present invention used for thermal abuse safety status monitoring of cylindrical lithium batteries;

[0030] Figure 11 This is a temperature test diagram used by the present invention to monitor the safety status of cylindrical lithium batteries subjected to thermal abuse. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below with reference to the accompanying drawings.

[0032] To overcome the shortcomings of the prior art, the present invention provides an oxidation-resistant, strain-insensitive flexible temperature sensor for lithium battery safety monitoring and its preparation method. This method is simple to prepare and utilizes wearable battery contact detection, improving detection accuracy while avoiding contact with the harsh internal battery environment, extending the sensor's service life, and enabling battery temperature monitoring and safety status monitoring.

[0033] This oxidation-resistant, strain-insensitive flexible temperature sensor for lithium battery safety monitoring includes a flexible substrate, an electrode, a temperature-sensitive layer, and a passivation layer, with the temperature-sensitive layer located between the passivation layer and the flexible substrate. The flexible electrode is patterned by vacuum evaporation and laser direct writing on the flexible substrate.

[0034] A method for preparing a flexible temperature sensor for lithium battery safety monitoring comprises the following steps:

[0035] A metal film is deposited on a flexible polyimide film using vacuum evaporation, and the film is patterned using a laser direct writing process to obtain electrodes;

[0036] The precursor ink of the temperature-sensitive layer is prepared by magnetic stirring and ultrasonic treatment, and then printed on the surface of a flexible substrate according to the designed pattern. The patterned precursor film is obtained by heating until the organic solvent evaporates, and then sintered in a tube furnace to obtain the temperature-sensitive material.

[0037] Synthesize polyamic acid slurry, spin-coat it on the temperature sensitive layer, and perform dehydration cyclization reaction of polyamic acid under heat to form a polyimide passivation layer;

[0038] Conductive silver paste is used as an adhesive between the electrode and the test wire. After the silver paste solidifies, an oxidation-resistant, strain-insensitive flexible temperature sensor for lithium battery safety monitoring is obtained.

[0039] Use polyimide tape to attach the flexible temperature sensor to the outer surface of the lithium battery with the passivation layer facing inward. Connect the test leads to the source meter to obtain the battery surface temperature in real time.

[0040] Specifically: The preparation of the flexible temperature sensor includes:

[0041] (1) Preparation of flexible interdigitated electrodes: A metal film is deposited on a flexible polyimide film by vacuum evaporation, and the film is patterned by laser direct writing to obtain interdigitated electrodes.

[0042] The metal film in step (1) has a thickness of 30 to 500 nm and is made of at least one of chromium, nickel, gold, platinum, and copper. Preferably, 10 nm of chromium and 100 nm of gold are evaporated. The laser direct writing parameters in step (1) are power of 5 to 15% and speed of 500 to 1000 mm / s. Preferably, the speed is 1000 mm / s and the power is 5%.

[0043] (2) Preparation of temperature-sensitive materials. Two-dimensional materials are prepared using inkjet printing technology. Ammonium tetrathiomolybdate and ammonium tetrathiotungstate are dissolved in deionized water, ethanol, ethylene glycol, and propylene glycol in appropriate proportions, and completely dissolved by ultrasonic and magnetic stirring to prepare ink. The polyimide substrate prepared with flexible interdigitated electrodes is cleaned with ultraviolet ozone, and the prepared ink is inkjet printed on the cleaned polyimide substrate. After the inkjet printing is completed, the organic solvent is removed by heating, and the material is sintered in a tube furnace to obtain a large area of ​​directly patterned two-dimensional molybdenum tungsten sulfur alloy thin film material on the polyimide surface. For example, the size of the temperature-sensitive film can be 11.6 mm × 5.5 mm.

[0044] The magnetic stirring speed in step (2) is 500-1000 rpm, and the stirring time is 60-120 min. Preferably, the magnetic stirring speed is 1000 rpm, and the stirring time is 80 min. The ultrasonic treatment time in step (2) is 10-60 min, and preferably the ultrasonic time is 60 min. The ultraviolet ozone cleaning time in step (2) is 300-600 s. Preferably, the cleaning time is 600 s. The temperature of the inkjet printing substrate in step (2) is 30-60°C, and the solvent evaporation time is 20-60 min. The number of inkjet layers is 15-20 layers, and the ink droplet spacing is 10-30 μm. Preferably, the number of printing layers is 20 layers, and the ink droplet spacing is 15 μm.

[0045] This method produces films with controllable thickness and good uniformity. Because inkjet printing allows for direct custom patterning, the material can be prepared quickly. After heating in a tube furnace, a molybdenum-tungsten-sulfur alloy film forms. This enables the fabrication of a flexible molybdenum-tungsten-sulfur alloy temperature sensor.

[0046] (3) Synthesis of polyamic acid slurry and encapsulation of polyimide. Based on the "two-step method", polycondensation polyamic acid was prepared. N2 was introduced into a three-necked flask for drying to ensure that the synthesis reaction was carried out under anhydrous conditions. TPEQ and DMF were added to the three-necked flask and stirred with a mechanical stirring shaft under N2 atmosphere until TPEQ was completely dissolved in the solvent, about 30 minutes. At this time, PMDA and DMF were quickly added to the system and continued to stir. After 10 minutes, the above steps were repeated twice (PMDA and DMF were quickly added to the system and continued to stir). After 2 hours, a light-colored, transparent, and viscous polyamic acid (PAA) solution was obtained. The polyamic acid solution was dripped onto the surface of the sensor temperature-sensitive material using a disposable rubber-tipped dropper and spin-coated. The spin-coated flexible temperature sensor was placed in an oven step and heated to remove the solvent in the film and to thermally imidize the polyamic acid to close the ring. After the thermal imidization was completed, the oven was opened and the sensor was allowed to cool naturally to room temperature to obtain a flexible temperature sensor encapsulated with polyimide film. The size of the passivation layer may be 15 mm x 8 mm.

[0047] The drying time during N2 drying in step (3) is 30-60 min. The spin coating parameters in step (3) are 500 rpm for 5 s and 4000-8000 rpm for 60 s. The step temperature increase in step (3) is programmed as follows: 70°C for 1 h, 150°C for 2 h, 200°C for 1 h, and 250°C for 1 h.

[0048] The flexible temperature sensor for lithium battery safety monitoring obtained through the above steps is tested: the flexible temperature sensor is tested for temperature performance at high temperature, high and low temperature cycling, and resolution. Lithium battery safety monitoring is also performed.

[0049] Example 1:

[0050] 10nm of chromium and 100nm of gold were deposited on a polyimide film by vacuum evaporation. The film was then patterned using a laser direct writing process to produce polyimide flexible interdigitated electrodes. Parameters were power 5 and speed 1000mm / s. 30mg of ammonium tetrathiomolybdate was dissolved in 1mL of deionized water, 1.5mL of propylene glycol, and 2.5mL of ethanol. The mixture was magnetically stirred at 1000rpm for 60 minutes and ultrasonically stirred for another 60 minutes. The polyimide flexible interdigitated electrodes were then cleaned in a UV-ozone cleaner for 10 minutes. The precursor solution was then inkjet-printed onto the treated polyimide film surface in 20 layers, with a droplet spacing of 15μm. The inkjet printer substrate temperature was 40°C and the nozzle temperature was 50°C. A square pattern (11.6mm x 5.5mm) was printed. After inkjet printing, the film was left on the substrate for 20-120 minutes to allow residual solvent to evaporate. The MoS2 thin film prepared by inkjet printing of customized pattern on flexible substrate was placed in a tube furnace at 450℃ in the atmosphere of Ar60sccm, H220sccm. Figure 1 As shown, the Raman spectrum Figure 2 The results show that the synthesized material is MoS2. PAA was spin-coated on the surface of the sintered MoS2 film with the following spin-coating parameters: 500 rpm for 5 seconds, 4000 rpm for 60 seconds. The film was then cured by step-by-step heating at 70°C for 1 hour, 150°C for 2 hours, 200°C for 1 hour, and 250°C for 1 hour. The encapsulated flexible temperature sensor was obtained as shown in the figure. Figure 3 As shown, the actual picture of the sensor is as follows Figure 4 The prepared MoS2 thin film flexible temperature sensor was tested for temperature performance, and its temperature sensing signal was as shown in Figure 5 As shown, high temperature strain performance tests were performed at 100℃, 200℃, and 300℃ with ε = 0.00286% - 0.02291%. The results are as follows Figure 6 As shown, it shows that the MoS2 thin film flexible temperature sensor is not sensitive to strain response. The oxidation resistance of the encapsulated and unencapsulated sensors was tested in air. The results are shown in Figure 7 As shown in the figure, it shows that the encapsulation greatly improves the antioxidant capacity of the sensor, and it is attached to the outer surface of the soft-pack lithium-ion battery as shown in the figure. Figure 8 , the soft pack lithium ion battery is subjected to 30V overcharge abuse, and the outer surface temperature of the soft pack battery is monitored in real time. The test results are as follows Figure 9 , the trend of the sensor is consistent with that of the thermocouple, indicating that the MoS2 thin film flexible temperature sensor can detect abnormal temperature changes on the surface of the soft-pack battery and can be used to monitor the thermal runaway of the soft-pack battery.

[0051] Example 2:

[0052] 20nm of chromium and 150nm of gold were deposited on a polyimide film by vacuum evaporation. The film was then patterned using a laser direct writing process to produce polyimide flexible interdigitated electrodes. Parameters were power 10 and speed 1000mm / s. 30mg of ammonium tetrathiomolybdate and 30mg of ammonium tetrathiotungstate were dissolved in 4mL of deionized water, 3mL of propylene glycol, and 5mL of ethanol. The mixture was magnetically stirred at 1000rpm for 80 minutes and further ultrasonically stirred for 60 minutes. The polyimide flexible interdigitated electrodes were then cleaned in a UV-ozone cleaner for 10 minutes. The precursor solution was then inkjet printed onto the treated polyimide film surface in 15 layers, with a droplet spacing of 20μm. The inkjet printer substrate temperature was 40°C and the nozzle temperature was 50°C. A square pattern (11.6mm x 5.5mm) was printed. After inkjet printing, the film was left on the substrate for 20-120 minutes to allow residual solvent to evaporate. The flexible substrate with customized inkjet printing pattern was placed in a tube furnace, and a molybdenum-tungsten-sulfur alloy film was prepared at 450°C under Ar60 sccm and H240 sccm. PAA was spin-coated on the surface of the sintered molybdenum-tungsten-sulfur alloy film with the spin-coating parameters of 500 rpm for 5s and 6000 rpm for 60s. The flexible temperature sensor was then packaged by performing step-by-step temperature curing at 70°C for 1h, 150°C for 2h, 200°C for 1h, and 250°C for 1h. Figure 10 , thermal abuse of cylindrical lithium-ion batteries at 100℃ and 150℃, real-time monitoring of the outer surface temperature of the cylindrical lithium-ion batteries, the test results are as follows Figure 11 , the trend of the sensor is consistent with that of the thermocouple, indicating that the MoS2 thin film flexible temperature sensor can detect abnormal temperature changes on the surface of cylindrical lithium-ion batteries and can be used to monitor thermal runaway of cylindrical lithium-ion batteries.

[0053] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0054] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0055] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A flexible temperature sensor for lithium battery safety monitoring, characterized in that: The sensor comprises a flexible substrate (1); Depositing an electrode (2) on the flexible substrate (1); Inkjet printing a temperature-sensitive precursor film on the electrode (2), and annealing to obtain a temperature-sensitive film (3); The surface of the temperature-sensitive film is covered with a passivation layer (4).

2. The flexible temperature sensor for lithium battery safety monitoring according to claim 1, characterized in that: The preparation of the temperature-sensitive film (3) includes: ammonium tetrathiomolybdate and / or ammonium tetrathiotungstate are dissolved in a mixed solvent of water, propylene glycol and ethanol to prepare ink; the prepared ink is inkjet printed on an electrode (2) of a flexible substrate (1) to form a precursor film; After removing the organic solvent from the precursor film, the precursor film is annealed at a temperature of 400-500° C. in an atmosphere of Ar 60 sccm and H 2 20-40 sccm to obtain a temperature-sensitive film (3).

3. The flexible temperature sensor for lithium battery safety monitoring according to claim 2, characterized in that: By volume ratio, the water:propylene glycol:ethanol=1:1.5:2.5; The amount of ammonium tetrathiomolybdate and / or ammonium tetrathiotungstate added is 6 mg / ml.

4. The flexible temperature sensor for lithium battery safety monitoring according to claim 2, characterized in that: The substrate temperature of the inkjet printing is 30-60° C., the solvent evaporation time is 20-60 minutes, the number of inkjet layers is 15-20 layers, and the ink droplet spacing is 10-30 μm.

5. The flexible temperature sensor for lithium battery safety monitoring according to any one of claims 1 to 4, characterized in that: The passivation layer (4) is a polycondensation type polyamic acid layer, and the preparation method includes: Under anhydrous and N2 atmosphere, TPEQ was completely dissolved in DMF, PMDA was added and stirred continuously, and the above steps were repeated twice to obtain a polyamic acid solution; The polyamic acid solution is spin-coated on the surface of the temperature-sensitive film (3), and then the temperature is raised to remove the solvent and to thermally imidize the polyamic acid to close the ring.

6. The flexible temperature sensor for lithium battery safety monitoring according to claim 5, characterized in that: The spin coating parameters are: 500 rpm, 5 s; 4000-8000 rpm, 60 s; The step heating was performed according to the program of 70°C, 1h, 150°C, 2h, 200°C, 1h and 250°C, 1h.

7. The method for preparing a flexible temperature sensor for lithium battery safety monitoring according to any one of claims 1 to 6, characterized in that: include: A polyimide film is used as a flexible substrate (1); Vacuum evaporation of metal thin film and laser direct writing to obtain electrodes (2); Mixing a reaction source and a solvent to form an ink, printing the ink on the electrode surface according to the designed pattern, heating until the organic solvent evaporates to obtain a patterned precursor film, and annealing to obtain a temperature-sensitive film (3); Based on the "two-step method" to prepare polycondensation polyamic acid, the polyamic acid is spin-coated on the surface of a temperature-sensitive film (3) and dehydrated and cyclized to form a polyimide passivation layer (4), thereby obtaining a flexible temperature sensor encapsulated by the polyimide film.

8. The method for preparing a flexible temperature sensor for lithium battery safety monitoring according to claim 7, wherein: The electrode (2) is an interdigitated electrode with a thickness of 30 to 500 nm, and the material is at least one of chromium, nickel, gold, platinum and copper; The temperature-sensitive film (3) covers the working ends of the interdigital electrodes.

9. The method for preparing a flexible temperature sensor for lithium battery safety monitoring according to claim 7, wherein: The laser direct writing parameter power is 5% to 15%, and the speed is 1000 mm / s.

10. The method for preparing a flexible temperature sensor for lithium battery safety monitoring according to claim 7, wherein: The preparation of the temperature-sensitive film (3) includes: Ammonium tetrathiomolybdate and / or ammonium tetrathiotungstate are dissolved in a mixed solvent of water, propylene glycol and ethanol to prepare ink; the prepared ink is inkjet printed on an electrode (2) of a flexible substrate (1) to form a precursor film; after removing the organic solvent from the precursor film, the precursor film is annealed at a temperature of 400 to 500° C. in an atmosphere of Ar 60 sccm and H 2 20 to 40 sccm to obtain a temperature-sensitive film (3); The passivation layer is a condensation-type polyamic acid layer, and the preparation method includes: Under anhydrous and N2 atmosphere, TPEQ was completely dissolved in DMF, PMDA was added and stirred continuously, and the above steps were repeated twice to obtain a polyamic acid solution; The polyamic acid solution is spin-coated on the surface of the temperature-sensitive film (3), and then the temperature is raised to remove the solvent and to thermally imidize the polyamic acid to close the ring.

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